Guest Post by Dave: PBXNSIP Trunking to OCS R2

This week I would like to introduce Dave Howe as guest technical contributor at VoIPNorm. Dave works at Microsoft as a UC Senior Support Engineer and is an aspiring technical writer (checkout Dave’s full profile under the new about page).). In my current role I don’t always get time to write in-depth technical articles so I will be leaning on Dave from time to time to keep technical content coming. Dave’s technical expertise is widely recognized at Microsoft and I am very privileged to have him contribute to the blog directly. You can also check out Dave’s blog at

This week is a quick post with info provided by Dave on trunking a PBXNSIP to OCS R2 using direct SIP for the purpose of routing calls between the two systems. Below is the trunk settings required for the PBXNSIP box.

Create New Trunk for OCS R2 Mediation Server

The option for creating a new trunk can be found in the lower left corner of the Trunks menu.

Enter an appropriate name for the new trunk and choose the SIP Gateway trunk type. Next, click on the Create button, which will add a new OCS 2007 R2 Mediation Server entry to the list of available trunks. To begin editing the configuration settings for the OCS 2007 R2 Mediation Server trunk, click on the edit option and configure the following values:

Name – OCS 2007 R2 Mediation Server
Type – SIP Gateway
Direction – Inbound and Outbound
Domain – (DNS name of Mediation Server)
Outbound Proxy –;transport=tcp (IP address of Mediation Server)
Override Codec Preference –G.711U (for North America) / G.711A (for Europe)
Lock Codec during Conversation – Yes
Accept Redirect – Yes
Interpret SIP URI always as Telephone Number – Yes
Is Secure – No
Send Call to Extension – {Leave Empty}
Assume that Call comes from User – {Leave Empty}
Ringback - Media

Be sure to scroll to the bottom of the screen and click Save. .
Finally, click on the List tab to return to the list of available trunks.

Look for more articles from Dave in the coming months.



  1. Hi Dave and Chris,
    For complete transparency, it is important to underline that this is neither supported nor recommended by Microsoft, and is provided for the purpose of lab experimentation only, to illustrate OCS' capabilities to interoperate in native, standard SIP with a variety of industry solutions.
    Only Direct SIP connections listed on the Open Interoperability Program page are tested and supported by Microsoft for use in production.
    Best regards

  2. Hello Dave and Chris,
    I agree with Francois, a clarification should be added. PBXnSIP is certified to be used with Exchange Server 2007 UM! It is not recommended / supported, but for Lab or Demo's the PBXnSIP can also perform Direct SIP or more advanced: DUAL FORKING! Please read if interested: - still works with OCS 2007 R2!
    btw: PBXnSIP is a spinoff by snom technology AG, Berlin Germany - who offers none-certified standard SIP based phones for Microsoft OCS 2007 RTM & R2. Don't forget: none of this is supported / recommended, even if it works for you or us :)
    Best regards,

    (atm: managing Microsoft CeBIT 2010 booth OCS/Exchange Infrastructure for the 4th time, lovin' it)

  3. Thanks for chipping in guys. I wont repeat whats already been said. I will make sure a disclaimer is added to additional posts for unsupported configurations.


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